This study will establish the usefulness and effectiveness of a singe dose of Bevacizumab administered intravenously (through the vein) in reducing the incidence of ARDS in individuals with severe sepsis (a condition characterized by an inflammatory response by the immune system throughout the whole body caused by infection) who are at high risk for the development of ARDS. All study participants will be randomized to receive placebo, bevacizumab 5 mg/kg or bevacizumab 10 mg/kg as a single intravenous dose in a double-blinded fashion in addition to traditional sepsis treatment.